French Patent # 2,945,785

In this 2009 patent, the redoubtable Franck Savard takes us back in time to the fork type derailleurs of the first half of the 20th century. The rear chain shifting unit has many features of Franck's EGS Up Cage, and the chain tensioner has a cunning ability to move with the chain line - but you can't help seeing similarities with the 1910 Terrot Numéro and the 1945 Overhill Two Speed to name but two of many candidates. This patent, itself, cites Henri-Michel Matocq's 1912 design as prior art.